Abradable strip coatings, of relatively complex structure for drive units are described in U.S. Pat. No. 3,042,365. Therein, the blade tips of moving blades abrade these abradable coatings, and the blades have, as a rule, only the hardness of the basic material of the blade or a blade coating and no specific application on the blade tip of an abrasive coating. Since the efficiency of compressors and turbines depends to a great extent on the size of the gap between the stator and the rotor, when there is increasing wear of the blade tips in a stripping process, this efficiency is reduced. The wear of the blade tips or of sealing tips on labyrinth seals is still further aggravated, if the strength and hardness of the abradable coatings is increased for increasing its resistance to erosion and/or for increasing its temperature stability. In this case, the blade tips or the sealing tips of the labyrinth seals must be coated with an abrasive.
Such an abrasive coating for blade tips is disclosed in U.S. Pat. No. 4,169,020. This abrasive coating comprises a metal matrix with particles of mechanically resistant material embedded in the matrix. Due to the high heat conductivity of the metal matrix material, there is a disadvantage that the structural part, namely the blade tip, can be overheated during the stripping process. Another disadvantage is that the particles of mechanically resistant material have no orientation and are randomly arranged in the matrix, so that the abrasion of the abradable coating by the abrasive coating is deficient as only a disordered scratching is produced on the abradable coating by the tips of the particles of mechanically resistant material. A determined reduction in the heat of friction is not provided with the abrasive coatings known in the art.